Wireless communication networks, including network nodes and radio network devices such as cellphones and smartphones, are ubiquitous in many parts of the world. These networks continue to grow in capacity and sophistication. To accommodate both more users and a wider range of types of devices that may benefit from wireless communications, the technical standards governing the operation of wireless communication networks continue to evolve. The fourth generation (4G) of network standards has been deployed, and the fifth generation (5G, also known as New Radio, or NR) is in development.
5G is not yet fully defined, but in an advanced draft stage within the Third Generation Partnership Project (3GPP). 5G wireless access will be realized by the evolution of Long Term Evolution (LTE) for existing spectrum, in combination with new radio access technologies that primarily target new spectrum. Thus, it includes work on a 5G New Radio (NR) Access Technology, also known as next generation (NX). The NR air interface targets spectrum in the range from below 1 GHz up to 100 GHz, with initial deployments expected in frequency bands not utilized by LTE. Some LTE terminology may be used in this disclosure in a forward looking sense, to include equivalent 5G entities or functionalities, although a different term is or may eventually be specified in 5G. A general description of the agreements on 5G NR Access Technology so far is contained in 3GPP TR 38.802 V0.3.0 (2016-10), of which a draft version has been published as R1-1610848. Final specifications may be published inter alia in the future 3GPP TS 38.2** series.
FIG. 1 depicts the major radio access technology (RAT) nodes in both LTE and NR, as presently defined. The base station in NR will be called gNB, corresponding to the eNB in LTE. These entities may communicate over a link similar to the X2 interface. A NextGen core in NR corresponds to the Evolved Packet Core (EPC) of LTE.
In addition to expanded bandwidth and higher bitrates to enrich User Equipment (UE) experience, the 5G NR technology will include expanded support for machine-to-machine (M2M) or machine type communications (MTC), variously known as the Networked Society or Internet of Things (IoT). This support focuses on optimized network architecture and improved indoor coverage for a massive number of radio network devices with the following characteristics: low throughput (e.g., 2 kbps); low delay sensitivity (˜10 seconds); ultra-low device cost (below 5 dollars); and low device power consumption (battery life of 10 years). As used herein, the term “radio network device” includes both UEs, such as cellphones and smartphones, and M2M/MTC/IoT type devices, which are often embedded in meters, appliances, vehicles, and the like, and are not directly controlled by users.
In all radio network device communication with the wireless network, uplink control signaling, also referred to as uplink L1/L2 control signaling, refers to time-critical signaling that is needed to convey control information from a radio network device to the network (i.e., in the uplink). Such control information may include, but is not limited to, Hybrid ARQ ACK/NACK feedback; channel quality information (CQI) including information that supports Multiple Antenna transmission and reception (MIMO); and Channel State Information (CSI), which can include information about the channel rank, often denoted with the term Rank Indication (RI). The control information may also include Scheduling Requests (SR) by which the mobile terminal can request transmission resources, e.g. triggered by user input, new data arriving to its transmission buffers, and the like.
In LTE, uplink control signaling is transmitted from a radio network device to the network either on the Physical Uplink Control Channel (PUCCH), or in case the control signaling is transmitted together with uplink data, multiplexed with the data on the Physical Uplink Shared Channel (PUSCH). Thus, the radio network device can transmit control signaling regardless of whether or not it has data to transmit simultaneously.
FIG. 2 depicts the LTE uplink control channel PUCCH. The PUCCH is arranged so that the physical resources that carry the PUCCH are at the upper and lower edges of the uplink carrier bandwidth. One benefit this arrangement is that all transmissions of data (e.g., PUSCH) of radio network devices can be arranged for transmission in contiguous spectrum simultaneously with radio network devices that transmit control signaling alone. Such PUSCH and PUCCH transmissions from different radio network devices are orthogonal in the sense they are transmitted on different time-frequency resources that do not interfere.
In particular, LTE configuration of PUCCH and PUSCH depicted in FIG. 2 also allows for configuring dedicated PUCCH resources to radio network devices, e.g., for periodic channel quality/state information, periodically occurring resources for scheduling requests, and the like.
In LTE, a radio network device does not use all PUCCH resources available on the carrier; rather, each radio network devices uses only a subset of PUCCH resources. In this manner, multiple radio network devices can send PUCCH control information to the network simultaneously. LTE therefore includes ways of subdividing the available resources of the control region for PUCCH, so many radio network devices can be allocated PUCCH resources within the same slot. For example, it is possible to configure radio network devices with dedicated PUCCH resources that occur periodically, e.g., for SR and CQI/CSI reporting. It can be anticipated that similar solutions, or at least solutions to achieve the same results, will be used in NR/5G.
Contiguous transmission can result in better Peak to Average Power Ratio (PAPR) and lower out-of-band emissions, as compared to non-contiguous transmissions—at least for the Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFTS-OFDM) used in the LTE uplink. As used herein, contiguous transmission means that the transmitter transmits on contiguous frequency bands, whereas non-contiguous means that a transmitter transmits on two or more frequency regions at the same time, with intervening frequency regions (e.g., guard bands in the case of carrier aggregation) where the transmitter does not transmit signaling (other than outskirts of the waveform).
As used herein, the term “control region” refers to spectrum within an uplink carrier nominally dedicated to uplink control signaling (although in some embodiments, data signaling may be allowed in control regions). PUCCH in LTE is one example of a control region. Non-contiguous data transmission could be necessary if a control region were to be placed at a central frequency region within the uplink carrier frequency. To avoid collision between radio network devices transmitting control signaling in the control region, and those radio network devices transmitting data, the data transmissions normally must not be allowed within the control region. This results in non-contiguous transmission for radio network devices transmitting data, if the devices utilize the full carrier bandwidth.
Having control regions (i.e., PUCCH) at the edges of the available uplink carrier bandwidth works well in LTE, where all radio network devices are required to support the full uplink carrier bandwidth. Having PUCCH at both edges also allows for frequency hopping between the regions, which provides frequency diversity gains, as illustrated by the shaded regions in FIG. 2. Since all radio network devices use the full transmission bandwidth, the control region is at the edges of the carrier for all radio network devices.
Since Release 10, LTE also supports carrier aggregation. With carrier aggregation, and particularly for uplink carrier aggregation, each aggregated uplink carrier has a structure similar to that described above, where control regions are placed at the edges of each carrier. Between each aggregated carrier, there is typically also a guard band for the purposes of aligning carriers on a carrier raster, and ensuring isolation between the uplink carriers—i.e., to ensure that transmitters on the different carriers do not interfere.
In the future, and particularly with the introduction of 5G/NR radio access technology, it is likely bandwidths will be defined even wider than the maximum 20 MHz carriers used in LTE. With bandwidths of, e.g., 40, 50, 100, 200 MHz, and even more than 1 GHz in high frequency spectra, there will be a need to support different types of radio network devices on the uplink carriers. In particular, there will be a need to support radio network devices that do not have the capability or need to transmit over the full uplink carrier bandwidth of, e.g., 100 MHz. A radio network device might have the capability of only transmitting over, e.g., 20 MHz, or the terminal might have the capability, but be currently configured to only transmit over 20 MHz. As another example, the network must support an anticipated explosion of narrowband radio network devices—for example, Narrowband Internet of Things (NB-IoT) utilizes the smallest allocable bandwidth unit in LTE: a Physical Resource Block (PRB), defined as 12 subcarriers by one slot (0.5 msec). With 15 KHz subcarrier spacing, NB-IoT radio network devices have a bandwidth of only 180 KHz. In these cases, the known solution from LTE, where the control regions are limited to the edges of wide uplink carrier bandwidth, are deficient.
Limiting at least some uplink carriers to smaller bandwidths, e.g., 5 MHz, will not alleviate the problem of radio network devices with still lower uplink bandwidth. For example, it is anticipated that many radio network device implementations will require low cost, and hence low maximum bit-rate, long battery life, and the like. Similar constraints (e.g., preserving battery life) may prompt radio network devices having higher capability to only transmit at a low bit-rate if that will satisfy current performance requirements.
FIG. 3 depicts one problem raised in supporting radio network devices utilizing less than a full uplink carrier bandwidth. Assume the uplink carrier bandwidth is 100 MHz, and a first radio network device transmits over the full 100 MHz. The first radio network device may transmit control signaling in the control regions at the carrier bandwidth edges, and (contiguous) data signaling throughout the remaining bandwidth. A second radio network device, however has only the capability, or is configured, to transmit over only a 20 MHz bandwidth. It is not possible to configure the second radio network device to utilize control regions at both edges of the 100 MHz carrier bandwidth. The second radio network device could use one of the control regions at either edge of the 100 MHz band if it would use one of the two corresponding sub-band portions of 20 MHz; however, the three 20 MHz sub-band portions in the middle of the 100 MHz carrier bandwidth would not be available for the narrower-bandwidth radio network devices, as these do not include any control region. This non-usability of much of the uplink carrier bandwidth, for radio network devices similar to the second one of FIG. 3, would severely limit the possibility of supporting both wide- and narrow-bandwidth radio network devices at the same time in the same network and/or in the same cells. It would also prevent the use of frequency hopping for narrower-bandwidth radio network devices between the control regions to achieve frequency diversity gains, as implemented and used in LTE.
Simply allocating control regions in the middle of the 100 MHz bandwidth presents a disadvantage to wide-bandwidth radio network devices, as it forces non-contiguous data transmission, which yields worse PAPR and out-of-band emissions.
The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.